Moran Eye Center Researcher Robert E. Marc: 2014 Paul Kayser Award In Retina Research

Our colleague and Director of Research at the University of Utah‘s Moran Eye Center, Robert E. Marc, Ph.D. has been named by the International Society for Eye Research as a recipient of the Paul Kayser International Award in Retina Research.  The award will be presented to Dr. Marc during the 2014 ISER Biennial Meeting of the Society for Eye Research in San Francisco, California on Thursday, July 24th, 2014.

The Paul Kayser International Award in Retina Research was created by the Directors of Retina Research Foundation and endowed by the Trustees of The Kayser Foundation to honor and perpetuate the memory of long-time friend and dedicated benefactor of RRF, Paul Kayser. Through this award both organizations are demonstrating the conviction they shared with Mr. Kayser that blindness caused by retinal disease is a global concern and must be addressed accordingly. It is thus the purpose of this award to foster greater awareness of the need for intensive study of the retina, its role in the visual process, and the retinal diseases that threaten and/or destroy eyesight by recognizing outstanding achievement and sustaining meritorious scientific investigations worldwide.

Dr. Marc was chosen as the recipient of this award for his lifetime body of work in retinal research, discovering the structure and function of the retina through novel technologies and approaches that have pushed our understanding of the retina forward.

A Synaptic Basis for Small World Network Design in the ON Inner Plexiform Layer of the Rabbit Retina

Bipolar cells_

This abstract was presented today at the 2014 Association for Research in Vision and Opthalmology (ARVO) meetings in Orlando, Florida by J Scott Lauritzen, Noah T. Nelson, Crystal L. Sigulinsky, Nathan Sherbotie, John Hoang, Rebecca L. PfeifferJames R. Anderson, Carl B. Watt, Bryan W. Jones and Robert E. Marc.

Purpose: Converging evidence suggests that large- and intermediate-scale neural networks throughout the nervous system exhibit small world’ design characterized by high local clustering of connections yet short path length between neuronal modules (Watts & Strogatz 1998 Nature; Sporns et al.2004 Trends in Cog Sci). It is suspected that this organizing principle scales to local networks (Ganmor et al. 2011 J Neurosci; Sporns 2006 BioSystems) but direct observation of synapses and local network topologies mediating small world design has not been achieved in any neuronal tissue. We sought direct evidence for synaptic and topological substrates that instantiate small world network architectures in the ON inner plexiform layer (IPL) of the rabbit retina. To test this we mined ≈ 200 ON cone bipolar cells (BCs) and ≈ 500 inhibitory amacrine cell (AC) processes in the ultrastructural rabbit retinal connectome (RC1).

Methods: BC networks in RC1 were annotated with the Viking viewer and explored via graph visualization of connectivity and 3D rendering (Anderson et al. 2011 J Microscopy). Small molecule signals embedded in RC1 e.g. GABA glycine and L-glutamate combined with morphological reconstruction and connectivity analysis allow for robust cell classification. MacNeil et al. (2004 J Comp Neurol) BC classification scheme used for clarity.

Results: Homocellular BC coupling (CBb3::CBb3 CBb4::CBb4 CBb5::CBb5) and within-class BC inhibitory networks (CBb3 → AC –| CBb3 CBb4 → AC –| CBb4 CBb5 → AC –| CBb5) in each ON IPL strata form laminar-specific functional sheets with high clustering coefficients. Heterocellular BC coupling (CBb3::CBb4 CBb4::CBb5 CBb3::CBb5) and cross-class BC inhibitory networks (CBb3 → AC –| CBb4 CBb4 → AC –| CBb3 CBb4 → AC –| CBb5 CBb5 → AC –| CBb4 CBb3 → AC –| CBb5 CBb5 → AC –| CBb3) establish short synaptic path lengths across all ON IPL laminae.

Conclusions: The retina contains a greater than expected number of synaptic hubs that multiplex parallel channels presynaptic to ganglion cells. The results validate a synaptic basis (ie. direct synaptic connectivity) and local network topology for the small world architecture indicated at larger scales providing neuroanatomical plausibility of this organization for local networks and are consistent with small world design as a fundamental organizing principle of neural networks on multiple spatial scales.

Support:  NIH EY02576 (RM), NIH EY015128 (RM), NSF 0941717 (RM), NIH EY014800 Vision Core (RM), RPB CDA (BWJ), Thome AMD Grant (BWJ).

The Role of NMDA Receptor Activity in Retinal Ganglion Cell Dendrite Development

Scientific poster example

 

This abstract was presented today at the 2014 Association for Research in Vision and Opthalmology (ARVO) meetings in Orlando, Florida by Eerik M. Elias, Ping Wang and Ning Tian.

Full size poster available here.

Purpose: To elucidate mechanisms underlying the dendrite developmental plasticity of retinal ganglion cells, we examined the role of glutamate receptors on retinal ganglion cell dendrite elongation and filopodia elimination.

Methods: We used the JamB genetically labeled subtype of RGCs as our working model. JamB-CreER:YFP ganglion cell dendritic arbors were imaged in whole mount retina using confocal microscopy. Dendrite length, area, branching, and filopodia number were traced and measured using Neurolucida. Visual inputs were blocked by dark-rearing pups after P5. Glutamatergic activity was blocked using daily intraocular injections of AP5 and CNQX from P9 to P13 or genetic ablation of the NMDA receptor in these RGCs.

Results: To test the role of visual inputs on dendrite development, we dark-reared mice from P5 to P30 and found a modest effect on filopodia elimination in JamB RGCs. Anticipating that spontaneous glutamatergic activity in the retina may also contribute to RGC filopodia elimination, we blocked spontaneous glutamatergic activity by daily intraocular injections of AP5 and CNQX from P9 to P13. This led to an increase in filopodia density due to decreased dendrite length but no change in filopodia number. We confirmed this result by examining NMDAR knockout JamB cells (JamB-CreER:YFP:Grin1-/-). As expected, Grin1-/- JamB RGCs have decreased dendrite outgrowth like the pharmacologic blockade. However, filopodia elimination in these cells was significantly decreased as well, suggesting that NMDA and non-NMDA glutamate receptors might regulate the RGC dendritic development in a differential manner. This effect was dramatic at P13. To test if this effect persists into adulthood, we examined Grin1-/- JamB RGCs at P30 and found that they are indistinguishable from wild-type JamB RGCs, suggesting that a compensatory mechanism exists to drive dendrite elongation and filopodia elimination in the absence of the NMDA receptor.

Conclusions: Our study demonstrated that ganglion cell dendrite outgrowth and pruning of filopodia require glutamatergic activity and visual input that act via NMDA and possibly non-NMDA glutamate receptors.

Portrait Of Vision Scientist: Stuart Mangel, Ph.D.

Stuart-Mangel

This image of Stuart Mangel was made in Berlin, Germany at the 2012 ISER meeting.  Stuart is Professor in the Department of Neuroscience at Ohio State University.  Stuart came out of John Dowling’s lab at Harvard and has contributed mightily to our understanding of synaptic plasticity, circadian rhythms and retinal circuitry/information processing in the retina.

Its amazing how few people in the CNS community make the link between brain and retina, but Stuart has been one of the strongest proponents of understanding CNS in the context of retinal study.  This is important not just from the perspective of the CNS, but also so that we have a fundamental understanding of how the retina works in health and disease.  Finally, Stuart’s lab is one of those few labs that also understands the importance behind an understanding of retinal circuitry, but also how that circuitry results in information processing.  His work in how directional selectivity functions will be critical in elucidating how neural systems handle data streams encoded through the visual system.

 

 

 

Image Credit: Bryan William Jones, Ph.D.

Building Retinal Connectomes

Connectomics image

There has been quite a bit of discussion of connectomes in the last while with President Obama’s new BRAIN initiative.  It is important to consider some of the requirements of obtaining a true synapse level wiring map in the brain as many are articulating from this initiative.  While there are new technologies that will be required to undertake this initiative for mapping the entire brain, the NIH NEI has been funding an ongoing project to study retinal circuitry which guides the community in how to approach a true synapse level map of the nervous system.

An example of this work  in Current Opinion in Neurobiology titled Building Retinal Connectomes is a review that illustrates the importance of having a complete network graph of connectivities in the retina and by extension other neural systems.  Complete network graphs are what will be required to understand how retinal systems (and any neural system) is constructed.  Even though the retinal community understands how retinas are wired in broad strokes, the precise, fine details are critical and elucidating them requires a new level of complete annotation derived from advances in light and ultrastructural imaging, data management, navigation and validation.

Authors are Robert E. Marc, Bryan W. Jones, J. Scott Lauritzen, Carl B. Watt and James R. Anderson.

 

Notable Paper: On Cone Bipolar Cell Axonal Synapses In The OFF Inner Plexiform Layer Of The Rabbit Retina

JCN cover 2013

This paper in the Journal of Comparative Neurology by  J. Scott Lauritzen, James R. Anderson, Bryan W. Jones, Carl B. Watt, Shoeb Mohammed, John V. Hoang and Robert E. Marc is another effort out of the Marc Laboratory For Connectomics that continues to define complete neural circuits to completeness.

This paper is another elucidation of data from the first Rabbit Retinal Connectome volume (RC1) that reveals that the division between the ON and the OFF inner plexiform layer (IPL) is not structurally absolute. ON cone bipolar cells make noncanonical axonal synapses onto specific targets and receive amacrine cell synapses in the nominal OFF layer, creating novel motifs, including inhibitory crossover networks. Automated transmission electron microscopic imaging, molecular tagging, tracing, and rendering of ∼400 bipolar cells reveals axonal ribbons in 36% of ON cone bipolar cells, throughout the OFF IPL. The targets include γ-aminobutyrate (GABA)-positive amacrine cells (γACs), glycine-positive amacrine cells (GACs), and ganglion cells. Most ON cone bipolar cell axonal contacts target GACs driven by OFF cone bipolar cells, forming new architectures for generating ON–OFF amacrine cells. Many of these ON–OFF GACs target ON cone bipolar cell axons, ON γACs, and/or ON–OFF ganglion cells, representing widespread mechanisms for OFF to ON crossover inhibition. Other targets include OFF γACs presynaptic to OFF bipolar cells, forming γAC-mediated crossover motifs. ON cone bipolar cell axonal ribbons drive bistratified ON–OFF ganglion cells in the OFF layer and provide ON drive to polarity-appropriate targets such as bistratified diving ganglion cells (bsdGCs). The targeting precision of ON cone bipolar cell axonal synapses shows that this drive incidence is necessarily a joint distribution of cone bipolar cell axonal frequency and target cell trajectories through a given volume of the OFF layer. Such joint distribution sampling is likely common when targets are sparser than sources and when sources are coupled, as are ON cone bipolar cells.

Figure Above: The first Rabbit Retinal Connectome volume (RC1), constructed via automated transmission electron microscopy (ATEM) and computational molecular phenotyping (CMP), spans the mid-inner nuclear layer (INL) at section 001 to the ganglion cell layer (GCL) at section 371, shown in a mirror image below. RC1 is a short cylinder ≈ 250 μm in diameter and ≈ 30 μm high containing 341 ATEM sections and 11 intercalated CMP sections. The cylinder is capped at top and bottom with 10-section CMP series allowing molecular segmentation of cells, and an activity marker, 1-amino-4-guanidobutane (AGB), to mark cells differentially stimulated via glutamatergic synapses. ATEM section 001 is a horizontal plane section through the INL visualized with GABA.glycine.glutamate → red.green.blue transparency mapping and a dark gold alpha channel (ANDed taurine + glutamine channels). ATEM section 371 is a horizontal plane section through the GCL visualized with GABA.AGB.glutamate → red.green.blue transparency mapping.

Happy Holidays 2012 And A Happy New Year In 2013

First Light Connectomics

We at Webvision would like to wish you all a very happy holiday season and a happy New Year in 2013.  Continuing on the theme from last years holiday season wishes, we have for you a colorful holiday image titled “Connectomics, First Light” from Robert E. Marc utilizing data generated by Scott Lauritzen, Crystal Sigulinsky and John Vo Hoang.

What we are seeing is a necklace of coupled retinal bipolar cells linked by sparse suboptical gap junctions, fundamentally new circuitry for retinal processing.  There is much more to this story, but we’ll wait until the publication.  For now, consider these data generated from the Connectomics project in the Marclab at the Moran Eye Center to be a colorful holiday image that represents our best wishes to you.

Seminar: Photoreceptor Networks And Color

Julie Schnapf, Ph.D. from University California San Francisco is delivering a seminar this Wednesday, September 12, 2012 at the Moran Eye Center auditorium on the first floor.  Julie will be talking about Photoreceptor Networks and Color.

Abstract:  Photoreceptors are more than just photon transduction machines.  They also communicate with each other, forming interactive electrical networks that increase visual sensitivity and create color-opponency.  These network interactions help explain some puzzling observations about color perception.

Notable Paper: Network Deficiency Exacerbates Impairment in a Mouse Model of Retinal Degeneration

This paper by Christopher W. Yee, Abduqodir H. Toychiev and Botir T. Sagdullaev examines the role that neural oscillations play in normal and pathological states.  In a neurodegenerative model of retinitis pigmentosa, the authors examined the activity of neural networks in the rd1 mouse model and compared that activity to the wild type.   Continue reading “Notable Paper: Network Deficiency Exacerbates Impairment in a Mouse Model of Retinal Degeneration”